At 11:53 PM -0500 2003/10/29, Barry Warsaw wrote:
Chuq, do you think it would be feasible for Mailman to try to handle that 90% itself, and then only hand-off to a Real MTA when it runs into trouble with the other 10% -- assuming it could know when it runs into trouble.
Bryan Costales and Eric Allman had this debate at InfoBeat/Mercury Mail. Bryan said that he could write a better "simple" MTA that could handle the easy 80% and leave the hard 20% to sendmail. Eric showed that he could improve sendmail to the point where it would perform at or near the level of performance of Bryan's code without throwing everything out, and would out-perform every other aspect of the system in question (so that the MTA was no longer the bottleneck at any stage).
I'm confident that the same sort of approach is appropriate for other well-respected MTAs (e.g., postfix, and exim in my personal experience).
Also, there's incoming SMTP and outgoing SMTP. It may be possible to build in support for one direction without providing the other. (It also may not be worth it.)
It's hard enough writing an incoming SMTP handler, and doing it right. Many large service providers have seriously screwed up when trying to do so (bigfoot anyone?), and others have only implemented half of the inbound solution (AOL), leaving the harder parts to standard programs like sendmail.
Even then I argued violently against this approach at AOL, and felt that we could do a better job by leaving all the external interfacing/queueing issues to sendmail, and instead make the in-house developed code an LMTP Local Delivery Agent. I was over-ruled, primarily because we had already gone too far down the road that had been chosen for us. Note that none of the original Internet Mail Operations team members are left at AOL (almost all bugged out when the new mail server software came online), and I don't think any of the original Internet Mail Development team members are left, either.
Bad Juju, Bwana.
I've been down this road before. Trust me, you don't want to do this.-- Brad Knowles, <brad.knowles@skynet.be>
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